WD External Hard Disk Drive Is Showing As Write-Protected In Windows XP x64

Hi,

I've recently had a massive computer failure that forced me to replace my mainboard and in the process I upgraded the processor and RAM as well.  I maxed out the RAM on the motherboard to 8 GB and in order to fully use that investment, I had to switch to a 64-bit OS.  I tried MS Vista x64 and found it to be completely and hopelessly inadequate as an operating system and singularly one of the worst failures to come out of Redmond since Windows ME.  Guiltily, I admit that I love the Aero interface but my fondness for the operating system ends there where my contempt of it begins full bore. . . but I digress.  I've now installed and am successfully up and running with Windows XP x64 but I have the strangest problem occurring and I'm hoping someone can help me out with it.

My system is kind of unique; I do a lot of video and audio editing and therefore I need a lot of storage space.  I have six internal hard drives and five external hard drives; all Western Digital totaling a little more than 5 TB of storage.  The internal drives are all great and no problems and mostly the externals are OK as well except that with each reboot it seems that a different external drive is showing up as write-protected.  I've not found a pattern to write-protection; it's almost as if they are being randomly write-protected.  Sometimes after a reboot only one drive will be write-protected sometime all five them are.  I can't remove files from or copy files to the drive; I receive an error:

Cannot copy xxxxxx: The disk is write-protected.
Remove the write-protection or use another disk.

The only thing is I didn't put the write-protection on there to begin with.

These drives all worked fine on the old motherboard with the 32-bit OS and I've even gone to the trouble of putting two shiny new USB 4 port PCI cards into the board that are dedicated to the external drives to make sure the problem wasn't with the motherboard itself and I get the same result.  I'm pretty sure the issue lies with the OS but I'm not sure how to fix it and since these drives are where more of my work is done; having them read only is costing me a truck load of money in terms of time by having to copy files that are GBs in size to different drives to be able to edit them.  I've searched Google and EE and I've seen this problem a lot with USB sticks, pen drives, CF cards, and other peripheral digital storage media but those problems %99.9999 percent of the time have involved someone accidentally engaging the write protection mechanism of the drive.  I thought maybe I'd done something like that when I rebuilt the machine but I've checked the drives and there doesn't seem to be a write-protect switch (not that I was surprised; I've never seen a hard drive with a write protect switch).  I can't find anyone that's had this issue with full blown hard drives.

Have any of you experienced anything like this and if so do you know how to fix it?  Or if you've never experienced it; do you have any ideas how I might fix it or start looking for a way to fix it?  I'm at my wits end and I can't go back to a 32-bit OS because I'll have wasted $300 on RAM.

Any help would be most appreciated.

PS:  I'm not sure if it's important or not but the new hardware I got is as follows: EVGA nForce 780i Triple SLI Mainboard with 8 GB of OCZ Reaper HPC UHP DDR2 RAM, an Intel Q6600 Core 2 Quad processor and a 620 Watt Enermax modular power deck (I double checked when I bought and it's more than enough to power everything I have; I'm not using SLI at the moment).  All my other peripherals I reused: my graphics card is an ASUS GeForce 8800 GTX with 768 MB (might have the size wrong here) of DDR3 VRAM; the hard drives I mentioned above and my CD/DVD ROM units.